sparc64: Remove locking of huge pages in DAX driver

sparc64: Remove locking of huge pages in DAX driver

Orabug: 25968141

Some huge page virtual addresses do not work with get_user_pages. Since
the purpose of calling get_user_pages is for its locking side effect, it
is not at all necessary for huge pages since they are permanently
pinned. So the failure is avoided and the unnecessary locking/unlocking
is eliminated.

Reviewed-by: Jonathan Helman <jonathan.helman@oracle.com>
Acked-by: Shannon Nelson <shannon.nelson@oracle.com>
Signed-off-by: Sanath Kumar <sanath.s.kumar@oracle.com>
Signed-off-by: Allen Pais <allen.pais@oracle.com>